I just ran into this problem and the listed solution fixed it for me too. I'm running the 6.0.8 version.

Just ran into this problem as well. Same version and worked well. I think the backup failed because the disk filled up and then it did not write the complete contents to the XML file. But renaming .old did the trick. Running full backup now...

Just ran into this problem as well. Same version and worked well. I think the backup failed because the disk filled up and then it did not write the complete contents to the XML file. But renaming .old did the trick. Running full backup now...

I had the same issue where backup failed due to disk filled up. But I can't rename the file as Ubuntu shows:

Bareword "accounts" not allowed while "strict subs" in use at (eval 1) line 1.